Private citizens can sue to enforce California's food labeling laws, the state Supreme Court said Monday in a ruling that revives a consumer complaint about the chemically induced orange coloring of salmon raised on fish farms.

Consumer lawsuits filed in 2003 and 2004 accused supermarket chains of misleading customers by failing to disclose on labels that the fish, naturally grayish, had been fed chemicals to give their flesh the color of wild salmon. Lower courts combined the cases and dismissed them, saying federal law barred states from allowing private suits over food labeling, but the state's high court unanimously disagreed and reinstated the claims.

The ruling "vindicates consumers' right to know what's in their food," said attorney Kevin Golden of the Center for Food Safety in San Francisco, which filed arguments in support of the plaintiffs.

Rex Heinke, lawyer for the supermarkets, said the ruling undermines the goal of Congress for national uniformity in food labeling laws and enforcement. He said the chains may appeal to the U.S. Supreme Court.

Farmed salmon take on the orange hue of their free-swimming kin after consuming the chemicals canthaxanthin and astaxanthin. Similar substances are also part of wild salmon's natural diet. The federal government does not consider them health hazards, and the plaintiffs are not claiming that consumers were harmed by eating farmed salmon.

But the suits contended that the stores induced some customers to pay higher prices for salmon and led others to buy fish they usually would have shunned because of the artificial coloring.

The suits were consolidated into a single case in Los Angeles and then dismissed by a trial judge and an appellate court. Those courts said that food labeling is regulated by federal law and that only the government, not private citizens, can sue for violations. Neither the federal government nor the state has acted in this case to enforce a federal law that requires disclosure of artificial food coloring.

But California's high court said Monday that a 1990 federal law - sponsored by Rep. Henry Waxman, D-Los Angeles - authorizes states to enact identical labeling requirements, which private citizens can enforce in court.

In this case, the court said, consumers are suing to require disclosure under a California labeling law and are not in conflict with the federal law.

After a similar suit was filed in Seattle in 2003, the nation's three largest supermarket chains, Safeway, Albertsons and Kroger, agreed to label their farm-raised salmon as artificially colored. Monday's ruling could lead to lower-court orders that would make such agreements legally binding in California.

Those three chains are defendants in the California case, along with Trader Joe's, Costco, Whole Foods, Bristol Farms and Ocean Beauty Seafoods.

Craig Spiegel, an attorney for the plaintiffs, said customers may also be entitled to damages for overpaying for farm-raised salmon and for buying fish because of misinformation.

Heinke, the supermarkets' lawyer, said the ruling was at odds with a federal law that was meant to leave enforcement in the hands of government regulators.

"We think Congress intended for the government to decide which (labeling standards) are worth enforcing and to ensure that the enforcement of statutes is uniform throughout the country," Heinke said. "You can't do that with private enforcement. ... You no longer have experts enforcing the law."